THE DURABILITY CHARACTERISTICS OF HIGH PERFORMANCE ...site.iugaza.edu.ps/relottol/files/HPC-Lecture-No.-1.pdf · directed toward high strength concrete but today the focus is more

THE DURABILITY CHARACTERISTICS OF HIGH PERFORMANCE CONCRETE

Dr. Ra’ed M. A. El- OttolDr. Ra’ed M. A. El- Ottol

M.Sc. Building TechnologyPh.D . Interior Design

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INTRODUCTIONINTRODUCTIONMost of the attention in the 1980s and 1990s was

directed toward high strength concrete but today the focus is more on concretes with high durability in severe environments resulting in structures with long life. (Bickley and Mitchell 2001)

Durability will become a key issue because we will become more and more concerned with sustainabledevelopment In that respect the use of high performance concrete is more ecological than the use of a usual concrete

























INTRODUCTIONINTRODUCTIONArchitects, engineers and constructors all over the world are

finding that using HPC allows them to build more durable structures at comparable cost. HPC is being used for buildings in aggressive environments, marine structures, highway bridges and pavements, nuclear structures, tunnels and pre cast.

Normal and special materials are used to make these specially designed concretes that must meet a combination of performance requirements. Special mixing, placing, and curingpractices may be needed to produce and handle high-performance concrete.




INTRODUCTIONINTRODUCTIONHPC can be made with cement alone or any combination of

cement and mineral components, such as, blast furnace slag, fly ash, silica fume, metakaolin, rice husk ash, and fillers, such as limestone powder

Not all properties can be achieved at the same time.

High-performance concretes are very sensitive to plastic and autogenous shrinkage, so that their use demands an immediate water curing. .













HPC is defined by the American Concrete Institute (ACI) as concrete meeting special combinations of performance and uniformity requirements that cannot always be achieved routinely using conventional and normal mixing, placing, and curing practices.

HPC is a concrete in which certain characteristics are developed for a particular application and environment Characteristics that may be considered critical for an application are ease of placement, compaction without segregation, early age strength, long-term mechanical properties, permeability, density, heat of hydration, toughness, volume stability, and long life in severe environments.

HSC is defined by ACI as concrete that has a specified compressive strength for design of 6,000 psi (41 MPa) or greater Therefore, HSC is an HPC in which the critical characteristic is a specified strength of 6,000 psi (41 MPa) or greater. Consequently, an HPC is always an HSC but not all HSC is HPC, because the durability property according to the previous definition of High performance concrete can be achieved with high strength or without. (Tumidajski and Chan 1996)




Durability schematically represented by the performance life function(Telford 1985)

Service life of concrete. A two- phase modeling of deterioration




Effect of plasticizers on the flowability of cement paste

(water:cement ratio = 0.3).







Deterioration Mechanisms

Physical deterioration, e.g. freeze-thaw action including deicing salts and the restraining effects of steep thermal gradients, cracking, abrasion and wear, or salt scaling due to recrystallization of salt in the pores where the expansive pressure of crystal growth leads to surface scaling of concrete of poor or mediocre quality and strength

Chemical deterioration, i.e. concrete reacting with the surrounding media causing either expansion of the concrete leading to cracking and spalling (alkali-silica reactions (ASR) or sulphates attack), or dissolution and disintegration of the cement paste which binds the fine and coarse aggregates together.

Electro-chemical deterioration, i.e. Corrosion having been depassivated either by carbonation or chloride contamination of the surrounding concrete, or a combination of both. Rust expansions cause cracking and spalling of the concrete. With restricted access of oxygen, such as under very moist conditions, black rust with very limited expansion my occur, leading to steel section reduction without the valuable warnings of cracks and spalling.




Deterioration Mechanisms

All deterioration depends on aggressive substances, including water, penetrating through the surface and accumulating in the outer layer and penetrating further into the bulk of the concrete.




Carbonation

Carbonation cannot be seen.Reaction between carbon dioxide with hydrated Ca(OH). formed CaCO,

Reduces the alkalinity of the concrete and can cause corrosion of reinforcement.




Mechanism of Frost damage in concrete

Critical saturation occurs when more than 91.7%of pores in concrete isfilled with water.

Water Expands 9% on freezing.







Freeze-Thaw Deterioration




Mechanism of Protection by AE




Mechanism of Protection by AE




1. Methods of Curing

Continuous wet curingPondingSprinklers/soaker hosesFogging (initial curing)

Curing coversPlastics and papersForms




1. Methods of Curing

Fogging Curing Of high performance concrete

Curing by wet burlap




SCO

PE O

F WO

RK

SC

OPE

OF W

OR

K

`

High Performance Concrete (HPC)

Strength Workability Durability

Introduction and definition

Workability performance

Strength performance

Workability characteristics

Strength characteristics

Freeze-Thaw

Corrosion

Carbonation Acid Attack

Sulfate Attack

Seawater Attack

Fire resistance

Analysis and Recommendation

Stop

Start

Alkali Reaction

Abrasion

Permeability

Durability characteristics

Introduction and definition




SCO

PE O

F WO

RK

SC

OPE

OF W

OR

K




ANALYSIS AND CONCLUSION ANALYSIS AND CONCLUSION

Part A: Durability Evaluation in Short period of time

In most of works and researches, the optimum compressive strength was achieved by adding 8% SF. However, as the silica fume content increased beyond 10%, the compressive strength decreased. (Bouzoubaa, Zhang et al. 2000)




ANALYSIS AND CONCLUSIONANALYSIS AND CONCLUSION




ANALYSIS AND CONCLUSIONANALYSIS AND CONCLUSION




P

∆

fy

fyk = P/ ∆

Strength of concrete with cementitious material and without




Shrin

kage

Str

ains

X 1

0-6

Time of Drying28 days 2 years

W/C = 0.7

W/C = 0.4

400

600




ANALYSIS AND CONCLUSION ANALYSIS AND CONCLUSION

Part B: Durability Evaluation in Long period of time

In most of works and researches, the optimum compressive strength was achieved by adding 8% SF. However, as the silica fume content increased beyond 10%, the compressive strength decreased.




The most appropriate curing regimes during the course of the hydration reaction.




Replacement levels of Pozzolans or slag needed to meet 0.10% 56-day expansion limit in C 441 tests. (Ferraris 1995)

1.High performance concrete and Alkali-Silica Reactivity (ASR).




Effect of cement replacements by mass with fly ash on abrasion erosion resistance of concrete at 28 days age




High performance concrete and Chloride permeability




Permeability according to air- entrainment




1.High performance concrete and Carbonation

The carbonation depth of concrete containing PFA and SF (Silica Fume) as partial cement replacements with w/b ratio of 0.27 at the age of 2 years increases with an increase in the PFA content. (dhir 2001)




High performance concrete and Fire resistance

the PFA and GGBS concretes were found to be able to retain theirproperties better at elevated temperatures and can be used in those places where there is a high risk of fire. The CFS concrete with more than 5% replacement should be avoided at such places due to the high risk of explosive spalling

Typical crack patterns observed in HPC at 800 ºC




5.5C3A (%)50C3S (%)28C2S (%)

Chemical Composition of Cement

1 day = 100%7 days= 50 %28 days= 10%

Moist Cured

First 12 – 36 hoursCritical Curing period2201 ft²/lb (450m²/kg). Fineness Type II, III (high early strength)Portland Cement Type30 to 31.5 CْAmbient temperature1.5 to 6%.air content50-58 cmSlump flow23-25 cmSlump 91 days Preferable Test age

OPTIMUM VALUE FOR HPCRECOMMENDED ITEM NAME




FLY ASH

7 -10 % Silica Fume / cement ratioDry and wet Class Silica Fume Type in HPC30 %Moisture content 3-4 %Fly ash MOI0.045 mm (Sieve No. 325)Fly ash fineness size

15 -25 % F20-35 % C50-70 if used water reducer

Fly ash/ cement ratioCLASS F, CFly Ash Type in HPC

0.25 - 0.35 %Water / cement ratio

2.5 - 2.7 FMFineness modulus of aggregate 13.2 to 26.5 mmCoarse Aggregate Size70Heat of hydration (kcal/kg)400Blaine Fineness (m²/kg)0.6Na2O equivalent (%)2-3SO3 (%)1.5-2.0MgO (%)9C4AF (%)




0.5>ARAbrasion resistance(AR=avg. depth of wear in mm)

1.0>SR>0.0Scaling resistance (SR=visual rating of the surface after 50 cycles)

60- 90%<F/TFreeze-thaw durability(F/t=relative dynamic modulus of elasticity after 300 cycles)

10.000-100.000 ohm.cmElectrical Resistivity Unit = Ohm. cm

1000>CPPermeability (CP=coulombs)

Long time ( to 12 days)Moisture and curing

Low temp. not advisedTemperature GGBFS concrete

Less than 3500 cm²/g GGBFS fineness size

25 -70 % Optimum. 50%

GGBFS / cement ratio

Class S , IS, M85GGBFS Type in HPC

Less than 0.01 mm1/100 opc

Silica Fume fineness size

7 -10 % Silica Fume / cement ratio




5-25 x 10 -2 per mlVolume pores diameterw/c 0.35

30/MPa>C( 0.21/psi>C)

Creep(C= icrostrain/pressurce unit)

400>SShrinkage(S=microstrain)

48 GPa <Ec(7x10 psi<Ec)

Elasticity(E=modulus of elasticity)

97MPa<fc( 14 Ksi<fc )

Strength (f=compressive strength)

600 mm<SF(24 in<SF)

Flowability (SL=slump,SF=slump flow)

SR<0.10 at 18 monthsSulfate Resistance (SR=expansion)(%)

0.10>ASR Alkali-silica reactivity (ASR=expansion at 56d) (%)

0 – 5 mmChloride penetration depth mm

500>CPChloride penetration(CP=coulombs)

5.000-10.000 ohm.cmElectrical Resistivity Ohm.cm




Ø High compression strength;

ØVery low porosity and absorbability .

Ø High durability and freeze resistance due to high tightness;

Ø Adhesion to the reinforcement increased by 40%;

Ø Shrinkage and creep reduced by 50%; being completed to 70% as

soon as the 7th day of curing;

Ø Increased heat of cement hydration and

Ø Reduced fire resistance because of high tightness, which makes it

impossible for the water contained in the hardened concrete to get out and

causes its transformation into high-pressure steam during a fire.

Conclusion Conclusion




Conclusion Conclusion q Much later strength gain between 28 days and 90 days or more. (With High performance concrete (HPC) concrete mixtures, the strength enhancement between 7 and 90-day often exceeds 150%,therefore it is unnecessary to overdesign them with respect to agiven specified strength.

q Superior dimensional stability and resistance to cracking from thermal shrinkage, autogenous shrinkage, and drying shrinkage. In unprotected concrete, a higher tendency for plastic shrinkage cracking .










Conclusion Conclusion q Better cost economy due to lower material cost and highly favorable lifecycle cost.

q Superior environmental friendliness due to ecological disposal of large quantities of fly ash, reduced carbon-dioxide emissions, and enhancement of resource productivity of the concrete construction industry.

q Consequently, properly cured High performance concrete (HPC) products are very homogenous in microstructure, virtually crack-free, and highly durable.




Conclusion Conclusion In conclusion, the High performance concrete (HPC) offers a holistic solution to the problem of meeting the increasing demands for concrete in the future in a sustainable manner and at a reduced or no additional cost, and at the same time reducing the environmental impact of two industries that are vital to economic development namely the cement industry and the coal-fired powerindustry.




HPC & PalestineHPC & Palestine

The technology of High performance concrete (HPC) is especially significant for countries like Palestine , where, given the limited amount of financial and natural resources, the huge demand for concrete needed for infrastructure and housing can be easily met in a Cost-effective and

Ecological Manner.




RECOMMENDATIONS RECOMMENDATIONS For Further StudiesFor Further Studies

Ø Researchers are also invited to improve HPC

ü Until now we still do not know how to make HPC with low permeability, but without high strength, designers have to learn to take advantage of the extra strength provided by low W / B ratio concrete. One day, we may be able to make durable concrete of low strength.







High performance concrete Confederation Bridge P.E.L




Two Union Square towers in Seattle




Kuala Lumpur City Center ( KLCC )










Documents

THE DURABILITY CHARACTERISTICS OF HIGH PERFORMANCE ...site.iugaza.edu.ps/relottol/files/HPC-Lecture-No.-1.pdf · directed toward high strength concrete but today the focus is more